热红外反射光谱技术在石英含量评价中的应用

张弘; 高鹏鑫; 高卿楠

doi:10.15898/j.cnki.11-2131/td.202104190053

热红外反射光谱技术在石英含量评价中的应用

Application of Thermal Infrared Reflectance Spectroscopy in the Evaluation of Quartz Content

摘要

摘要: 石英是热液矿床重要的找矿标志，也是影响页岩气储层可压裂性评价的关键性因素，目前主要利用X射线衍射方法和扫描电镜矿物定量分析方法进行实验室内石英定量分析。为满足野外钻井现场进行快速、大批量矿物定量分析的需求，本文以羌塘盆地泥岩、砂岩、砾岩、灰岩和白云岩等沉积岩样品为研究对象，应用热红外反射光谱技术和综合自动矿物岩石学（QEMSCAN）矿物定量分析技术，开展了石英热红外反射光谱含量评价研究。结果表明：石英在8625nm、12640nm和14450nm三个特征中心波长位置的相对深度（D₈₆₂₅、D₁₂₆₄₀、D₁₄₄₅₀）可以用来区分陆源碎屑岩和碳酸盐岩，当D₈₆₂₅>0.14或D₁₂₆₄₀>0.02或D₁₄₄₅₀>0.02时，样品岩性主要为陆源碎屑岩，否则主要为碳酸盐岩。此外，D₈₆₂₅、D₁₂₆₄₀、D₁₄₄₅₀三个石英光谱特征参数均与石英含量具有高度的相关性，均可以利用最小二乘法构建石英含量评价模型。以拟合优度（R²）和均方根误差（RMSE）两个指标评价三个模型的精度，其中根据D₈₆₂₅参数建立的石英含量估算模型的拟合优度最大（R²=0.9237），且均方根误差最小（RMSE=8.51），基于此认为D₈₆₂₅石英光谱参数可以作为评价石英含量的最优光谱指标。本文基于热红外反射光谱技术建立的该种野外快速估算钻井中石英含量的方法，为热液矿床找矿勘查和页岩气勘探开发提供了借鉴和参考。

Abstract:
BACKGROUNDQuartz is not only an important prospecting indicator of hydrothermal deposits, but also a key factor affecting the evaluation of shale gas reservoir fracturing. It is of great significance to carry out the rapid evaluation of quartz content in field drilling. However, the analysis process of conventional methods (X-ray diffraction method and scanning electron microscope) is relatively long.
OBJECTIVESTo establish a rapid and large-scale quantitative evaluation model of quartz based on thermal infrared reflectance.
METHODSHandheld FTIR spectrometer and mineral quantitative analyzer were used to analysis the content and characteristic absorption peak intensity of quartz, from mudstone, sandstone, conglomerate, limestone and dolomite samples in the Qiangtang Basin.
RESULTSThe relative depth (D₈₆₂₅, D₁₂₆₄₀, D₁₄₄₅₀) of quartz at the three characteristic center wavelength positions of 8625nm, 12640nm and 14450nm can be used to distinguish terrigenous clastic rocks from carbonate rocks. When D₈₆₂₅>0.14 or D₁₂₆₄₀>0.02 or D₁₄₄₅₀>0.02, the samples are mainly terrigenous clastic rocks. In addition, three quartz spectral characteristic parameters D₈₆₂₅, D₁₂₆₄₀, and D₁₄₄₅₀ all have a high correlation with the quartz content, and the least square method can be used to construct a quartz content evaluation model. Two indicators of goodness of fit (R²) and root mean square error (RMSE) were used to evaluate the accuracy of the three models. Among them, the quartz content estimation model based on D₈₆₂₅ parameters had the highest goodness of fit (R²=0.9237), with the smallest root square error (RMSE=8.51). Based on this, it is believed that the D₈₆₂₅ quartz spectral parameters can be used as the optimal spectral index for evaluating the quartz content.
CONCLUSIONSBased on thermal infrared reflectance spectroscopy technology, a field method for quickly estimating the content of quartz in drilling core has been established, which provides reference for prospecting and exploration of hydrothermal deposits and shale gas exploration and development.

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